Device and method for deployment of an anchoring device for intervertebral spinal fusion

ABSTRACT

A device and methods for intervertebral spinal fusion of adjacent intervertebral bodies. An intervertebral spacer is positioned within a narrow disc space between adjacent intervertebral bodies of a patient. The spacer is arranged with upper and lower guides. The guides are adapted to simultaneously guide the deployment of upper and lower anchors of an anchoring device into their respective intervertebral bodies. The spacer is also adapted to lock the upper and lower anchors to the spacer in the deployed position.

FIELD OF THE INVENTION

The present invention relates generally to intervertebral spacers for fusing adjacent vertebras, and more particularly to a device and methods for doing so.

BACKGROUND

Intervertebral spinal fusion is well known in the art. In the prior art, an intervertebral spacer is implanted between two adjacent intervertebral bodies. The spacer allows a surgeon to deposit bone graft between the problem vertebras in order to fuse the vertebras together. To achieve proper fusion, the implanted spacer must be securely anchored between the vertebras such that there is little to no movement once implanted. Protrusions arranged on the superior and inferior surfaces of the spacer provides a means to stabilize the spacer between the vertebras. However, it has been discovered that spacers stabilized in this way may still move due to the stress exerted on the implanted spacer when the patient moves. Other commonly employed stabilizing techniques include pedicle screws and rods. In this technique, pedicle screws are independently screwed into two or three spine segments. A short rod is then used to connect the pedicle screws to prevent motion at the segments that are being fused. However, this technique is time consuming because the pedicle screws need to be independently screwed into the vertebras. It also requires the surgeon to make large/numerous incisions in the patient to insert the pedicle screws. Because of these deficiencies in the prior art, there exists a need to provide a more effective and efficient way of stabilizing adjacent vertebras in the field of intervertebral spinal fusion.

SUMMARY

For the purpose of the following description and the appended claims, “proximal” and its inflected forms are defined as the part, portion, section, etc., of an object that is closest to the person using that object.

For the purpose of the following description and the appended claims, “distal” and its inflected forms are defined as the part, portion, section, etc., of an object that is furthest away to the person using that object.

The present invention provides a way to stabilize adjacent vertebras without some of the deficiencies of the prior art discussed above. In the illustrative embodiment of the present invention, a spacer is provide with an upper guide and a lower guide. The upper and lower guides are adapted to guide the simultaneous deployment of a respective upper anchor and lower anchor of an anchoring device when force is applied thereto. More precisely, force is simultaneously applied to a proximal portion of the upper and lower anchors. The force simultaneously deploys the upper and lower anchors into their respective intervertebral bodies. The upper and lower anchors are constructed and dimensioned in such a way to pierce and penetrate into their respective vertebras. The combination of the anchors and the protrusions arranged on the surfaces of the spacer provides additional stabilization of the implanted spacer. These advantages of the present invention will be apparent from the following disclosure and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts a perspective view of an intervertebral spacer in accordance with an illustrative embodiment of the present invention;

FIG. 1B depicts another perspective view of the intervertebral spacer of FIG. 1A;

FIG. 2A depicts a top view of the intervertebral spacer of FIGS. 1A and 1B;

FIG. 2B depicts a side view of the intervertebral spacer of FIGS. 1A and 1B;

FIG. 3A depicts one side of an anchor in accordance with an illustrative embodiment of the present invention;

FIG. 3B depicts the other side of the anchor of FIG. 3A;

FIG. 4A depicts two anchors being loaded into the intervertebral spacer of FIGS. 1A and 1B;

FIG. 4B depicts the two anchors of FIG. 4A loaded into the intervertebral spacer of FIGS. 1A and 1B, the two anchors being in an undeployed state;

FIG. 5A depicts a perspective view of an implantation instrument in accordance with an illustrative embodiment of the present invention;

FIG. 5B depicts a cross-sectional view of the implantation instrument of FIG. 5A, the cross-sectional view depicting a narrower section and a wider section of the implantation instrument;

FIG. 5C depicts an exploded, cross-sectional view of the wider section of the implantation instrument of FIG. 5A;

FIG. 5D depicts a cross-sectional view of the implantation instrument gripping the lateral surfaces of the intervertebral spacer of FIGS. 1A and 1B;

FIG. 6A depicts the implantation instrument of FIG. 5A having deployed the anchors of FIG. 4A;

FIG. 6B depicts an exploded, top view of the deployed anchors of FIG. 6A;

FIGS. 6C and 6D depict an exploded, perspective view of the deployed anchors of FIG. 6A;

FIG. 7A-7C depict a spacer and anchor in accordance with an alternative embodiment of the present invention, wherein the upper and lower anchors of the anchoring device form a single, unitary piece;

FIG. 8A-8C depict a spacer and anchor in accordance with an alternative embodiment of the present invention, wherein the upper and lower anchors of the anchoring device are disposed entirely within the spacer;

FIG. 9A-9H depict an upper anchor and a lower anchor arranged on a drive plate in accordance with an alternative embodiment of the present invention; and

FIG. 10 depicts a spacer having worm gear for deploying one or more anchors in accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION

FIGS. 1A and 1B depict perspective views of intervertebral spacer 100 in accordance with an illustrative embodiment of the present invention. Spacer 100 generally has a rectangular shape, but the present invention is not limited to such a shape. Spacer 100 can have any shape, size, or combination thereof to meet the needs of a spinal fusion candidate.

As depicted in FIGS. 1A and 1B, spacer 100 comprises superior surface 102, inferior surface 104, lateral surfaces 106 and 108, distal portion 110, and proximal portion 112. Inferior surface 104 is a mirror image of superior surface 102 and lateral surface 108 is a mirror image of lateral surface 106. Spacer 100 is preferably formed from titanium alloy but other biocompatible materials (e.g., polyetheretherketone (PEEK), other surgical grade metals, alloys, or a combination thereof) can also be used to form spacer 100.

Beginning at distal portion 110, spacer 100 is constructed to have a tapered end that narrows towards the distal most end. This design helps facilitate easier entry of spacer 100 into the narrow disc space arranged between two adjacent vertebral bodies.

To fuse the adjacent vertebras together, bone graft is used. For this purpose, the body of spacer 100 is provided with through-hole 114. The through-hole extends through the center of surfaces 102, 104, 106, and 108 and is adapted to receive the bone graft for fusing the adjacent vertebras. In the illustrative embodiment, through-hole 114 generally has a rectangular shape. However, those skilled in the art will appreciate after reading this disclosure that through-hole 114 can have any shape, size, or a combination thereof. As further depicted in FIGS. 1A and 1B, surfaces 102 and 104 are provided with a plurality of protrusions or teeth 116 to help prevent spacer 100 from expulsion after being implanted between the adjacent vertebras. It will be appreciated by those skilled in the art, after reading this disclosure, that teeth 116 can be angled in any number of degrees (e.g., 45°, 90°, etc.) and can have any number of orientations without departing from the scope of the present invention. Through-hole 114 and teeth 116 can be seen more clearly in FIGS. 2A and 2B.

Turning now to proximal portion 112, upper and lower guides are provided to respectively guide the deployment of upper anchor 118 and lower anchor 120 into their respective vertebral bodies. The upper and lower anchors will be discussed in more detail below, with respect to FIGS. 3A and 3B. In the illustrative embodiment, the upper guide is characterized by an upper inclined surface 122 (e.g., a curvilinear surface, etc.) and an upper pair of oppositely positioned lateral recesses 124. Because the lower guide is a mirror image of the upper guide, the lower guide is also characterized by a lower inclined surface 126 and a lower pair of oppositely positioned lateral recesses 128. The upper and lower pair of lateral recesses 124 and 128 are dimensioned to respectively complement the arc, curvature, etc., of the upper and lower anchors. An advantage of recesses 124 and 128 is that they ensure that their respective anchors maintain a desired trajectory when impacted by an anchor driver. The recesses 124 and 128 also prevent their respective anchors from egressing out of spacer 100 when impacted by the anchor driver. These features and their advantages will be discussed in more detail below, with reference to FIGS. 4A and 4B.

Proximal portion 112 also comprises a pair of oppositely positioned lateral chamfers 130 and 132. Each of the lateral chamfers has a sloping edge and is positioned proximally to their respective locking recesses 134, 136, 138, and 140. As will be described in more detail below, with reference to FIGS. 6A-6D, the chamfer-recess combination is a mechanism that allows upper anchor 118 and lower anchor 120 to be locked to spacer 100 after deployment. It will be appreciated by those skilled in the art, after reading this disclosure, that locking recesses 134, 136, 138, 140 could be detents in some embodiments and through-holes in other embodiments.

Proximal portion 112 further comprises lateral surfaces 142 and 144 that are respectively constructed with gripper recesses 146 and 148. The gripper recesses are dimensioned and arranged to receive corresponding ribs of an implantation instrument employed by a surgeon. The ribs are adapted to fit squarely into their corresponding recesses so that spacer 100 can be securely gripped by the surgeon. It should be noted that gripping the spacer with an implantation instrument serves at least two purposes. First, it enables the surgeon to more easily orient spacer 100 in a desired position within the narrow disc space of the adjacent vertebras. Secondly, it prevents spacer 100 from coming free from the implantation instrument while the surgeon is impacting the upper and lower anchors with an anchor driver. Although each of the lateral surfaces is depicted as having three gripping recesses, it will be appreciated by those skilled in the art that each of the lateral surfaces can have more or less gripper recesses than depicted. This feature of the present invention will be described in more detail below, with reference to FIGS. 5A-5D.

FIGS. 3A and 3B are perspective views of an anchor in accordance with an illustrative embodiment of the present invention. Since upper anchor 118 and lower anchor 120 have substantially the same physical and functional characteristics, thus being interchangeable, the following discussion of FIGS. 3A and 3B will use the word “anchor” to describe both the upper and lower anchors. Further, it should be noted that upper anchor 118 and lower anchor 120 (whether formed as independent pieces or as a single unitary piece) collectively define an anchoring device.

FIG. 3A depicts the surface of an anchor that is adapted to slide along an inclined surface of a guide (e.g., upper inclined surface 122 or lower inclined surface 126). In the illustrative embodiment, the anchor is constructed to have a curved or semi-curved surface that is contoured to be substantially the same as the inclined surface of the guide it slides on. The surface of the anchor is preferably smooth throughout its length in order to reduce the amount of friction drag produced when the surface slides along the inclined surface.

The anchor also comprises a pair of oppositely positioned lateral sides 302 and 304, which are adapted to slide into their respective lateral recesses (e.g., upper lateral recesses 124 or lower lateral recesses 128). The anchor is also constructed with a pair of flexible prongs 306 and 308, which respectively comprises lateral projections 310 and 312. The flexible prongs and lateral projections work in cooperation to lock the anchor to spacer 100 in a deployed position. The lateral sides, flexible prongs, and lateral projections of the anchor are also depicted in FIG. 3B.

To enable the anchor to penetrate a vertebral body, distal portion 314 of the anchor is tapered to form an edge. Since the anchor is made of titanium alloy, the distal portion of the anchor is sufficiently strong to pierce and penetrate through the endplate of the vertebral body. Although the anchor is preferably formed from titanium alloy, other biocompatible materials (e.g., polyetheretherketone (PEEK), other surgical grade metals, alloys, or a combination thereof) can be used to form the anchor.

It will be clear to those skilled in the art that the foregoing discussion of FIGS. 3A and 3B applies to both upper anchor 118 and lower anchor 120.

FIG. 4A depicts upper anchor 118 and lower anchor 120 being loaded into spacer 100. As discussed above, the upper guide of spacer 100 has an upper pair of oppositely positioned lateral recesses 124. Each lateral recess 124 is adapted to receive a respective one of lateral sides 302 and 304 of upper anchor 118. Similarly, the lower guide of spacer 100 has a lower pair of oppositely positioned lateral recesses 128 (shown more clearly in FIG. 1B). Each lateral recess 128 is adapted to receive a respective one of lateral sides 302 and 304 of lower anchor 120. Turning now to FIG. 4B, this figure depicts spacer 100 loaded with the upper and lower anchors. In FIG. 4B, upper anchor 118 and lower anchor 120 are in an undeployed state and are disposed entirely within spacer 100. That is, no part of upper anchor 118 and lower anchor 120 extend beyond the profile of teeth 116 arranged on spacer 100. In the loaded/undeployed state, spacer 100 is ready to be gripped by an implantation instrument for simultaneous deployment into their respective intervertebral bodies.

FIG. 5A is a perspective view of implantation instrument 500, which comprises, inter alia, housing 502, anchor driver 504, handle 506, and a pair of oppositely positioned grippers 508 and 510. As will be discussed in more detail below, with reference to FIGS. 5B-5D, anchor driver 504 can be advanced forwards or retracted backwards via handle 506 to respectively grip or release spacer 100.

FIG. 5B is a cross-sectional view of the implantation instrument of FIG. 5A. As shown in this view, housing 502 is divided into two sections—namely, a narrower section 512 and a wider section 514. Anchor driver 504 is constructed to fit squarely into narrower section 512 with little or no lateral and radial movement, while the area of wider section 514 is dimensioned to accommodate the width of anchor driver 504 and a pair of adjacently positioned, oppositely bowed leaf springs 516 and 518.

In the configuration depicted in FIG. 5B, anchor driver 504 can be advanced forwards towards leaf springs 516 and 518 via handle 506. As the forward advancement causes anchor driver 504 to be wedged between leaf springs 516 and 518, their respective grippers 508 and 510 will begin to simultaneously pivot inward to clamp onto the lateral surfaces of spacer 100.

More precisely, and with reference to FIG. 5C, the forward advancement of anchor driver 504 causes gripper 508 to pivot inwardly about pivot point 520. This pivot action is a result of leaf spring 516 being compressed outwards towards the wall of housing 502 as anchor driver 504 engages the bowed portion of leaf spring 516. As gripper 508 pivots inwards, ribs 524 engage their respective gripper recess 146 (depicted in FIG. 1A) arranged on spacer 100. Likewise, gripper 510 will pivot inwardly about pivot point 522 in response to the forward advancement of the driver, resulting in ribs 526 engaging their respective gripper recess 148 (depicted in FIG. 1B). By means of the foregoing, spacer 100 can be securely gripped by implantation instrument 500, as depicted in FIG. 5D.

As depicted in FIG. 5D, the head of anchor driver 504 stops at or slightly before the distal end of housing 502 after gripping spacer 100. While spacer 100 is being gripped by implantation instrument 500, spacer 100 is positioned within the narrow disc space between adjacent vertebras. Continuing to grip spacer 100 with implantation instrument 500, the surgeon removes cap 530 and is now ready to impact handle 506 with a weighted object (e.g., hammer, mallet, etc.). In accordance with the illustrative embodiment, cap 530 has two functionalities. First, cap 530 when attached to handle 506 disallows forward movement of anchor driver 504 past a certain point—namely, the distal end of housing 502. Secondly, cap 530 prevents inadvertent deployment of upper anchor 118 and lower anchor 120 during positioning of spacer 100 within the adjacent vertebral bodies.

When the surgeon impacts handle 506 with a weighted object, anchor driver 504 is driven forwards into the proximal portion of upper anchor 118 and lower anchor 120, thereby simultaneously deploying the anchors into their respective vertebras. The surgeon may impact handle 506 one or more times so that the anchors reach a desired depth within their vertebras, and so that the anchors engage the locking feature of the present invention described in more detail below. Once upper anchor 118 and lower anchor 120 is locked to spacer 100 in the deployed position, the surgeon can retract anchor driver 502 so that leaf springs 516 and 518 can return to their relaxed state. While returning to their relaxed state, grippers 508 and 510 will begin to pivot outwardly to disengage from their gripper recesses, thereby releasing spacer 100.

FIG. 6A depicts a perspective view of implantation instrument 500 in which driver anchor 504 has simultaneously deployed upper anchor 118 and lower anchor 120. As discussed above, the head of anchor driver 504 is simultaneously driven into the proximal portion of upper anchor 118 and lower anchor 120 as the surgeon impacts handle 506. This causes both the upper anchor 118 and lower anchor 120 to independently slide along the upper inclined surface 122 and lower inclined surface 126, respectively. The upper and lower inclined surfaces respectively press against the surface of the upper and lower anchors (i.e., the surface depicted in FIG. 3A) to deploy the anchors into their respective vertebral bodies. FIGS. 6B-6D depict upper anchor 118 and lower anchor 120 simultaneously deployed after being impacted by anchor driver 504. As shown in these figures, the distal ends of upper anchor 118 and lower anchor 120 in the deployed state are radially extended outside of spacer 100. That is, the distal ends of upper anchor 118 and lower anchor 120 extend past the height of teeth 116 of spacer 100 after being deployed.

From the foregoing discussion, it will be clear to those skilled in the art that upper anchor 118 and lower anchor 120 are separate elements that slide independently of each other along their respective upper and lower guides. It will also be clear from the foregoing discussion that an advantage of using the upper and lower anchors of the present invention is that they provide additional anchorage for stabilizing a spacer. In other words, not only is the spacer anchored to the intervertebral bodies via its teeth, the spacer is also provided with additional anchorage by the upper and lower anchors, since they extend past the profile of the teeth and therefore penetrating deeper into the intervertebral bodies.

Returning to FIGS. 6C and 6D, these figures depict upper anchor 118 and lower anchor 120 locked to spacer 100 in a deployed position. Since upper anchor 118 and lower anchor 120 are locked to spacer 100 in substantially the same way, the following discussion of FIGS. 6C and 6D will use the word “anchor” to describe both the upper and lower anchors.

As the anchor is impacted by driver 504, lateral projections 310 and 312 will respectively engage the sloping edge of lateral chamfers 130 and 132. Lateral chamfers 130 and 132 are depicted in the figures as being arranged proximally to locking recesses 134, 136, 138, and 140 of spacer 100. The pressure and force of the impact causes flexible prongs 306 and 308 to flex laterally inwardly. As lateral projections 310 and 312 past their respective lateral chamfers, flexible prongs 306 and 308 will return to a relaxed state, thereby causing lateral projections 310 and 312 to laterally extend into their corresponding locking recess 134, 136, 138, and 140. This locking feature of the present invention prevents the anchors from disengaging from spacer 100 after being deployed into the vertebral bodies.

It will be clear to those skilled in the art, after reading this disclosure that numerous modification can be made to the illustrative embodiment without departing from the scope of the invention. For example, in one alternative embodiment, upper anchor 118 and lower anchor 120 can be constructed as a single unitary piece. FIGS. 7A-7C depict such an anchoring device.

As depicted in FIG. 7A, upper anchor 702 of anchoring device 700 comprises underside 704 that is adapted to press against upper inclined surface 706 of the upper guide arranged on spacer 100. Similarly, lower anchor 708 of anchoring device 700 comprises underside 710 that is adapted to press against lower inclined surface 712 of the lower guide arranged on spacer 100. As anchoring device 700 is advanced forwards, pressure causes the undersides to press against their respective inclined surfaces, which guides upper anchor 702 and lower anchor 708 to radially and simultaneously deploy into their respective vertebral bodies. As depicted in FIGS. 7B and 7C, upper anchor 702 and lower anchor 708 extend past the profile of teeth 714 to provide additional anchorage. Once the upper and lower anchors have been simultaneously deployed into their vertebra, locking cap 716 can be used to lock the anchors in their deployed position. Specifically, locking cap 716 is adapted to press the proximal end of anchoring device 700 to lock the anchoring device to spacer 100.

In another embodiment, as depicted in FIGS. 8A-8C, spacer 100 houses both upper anchor 802 and lower anchor 804. In other words, both the upper and lower anchors are disposed entirely within spacer 100 when the anchors are in a relaxed state. As shown in FIG. 8B, an internal drive screw 806 (i.e., an anchor drive) can be turned so that wedge 812 can be advanced forwards towards the bowed portion of both upper anchor 802 and lower anchor 804. Wedge 812 is forcibly advanced towards the bowed portion to simultaneously force upper anchor 802 and lower anchor 804 to extend through an opening arranged on superior surface 808 and inferior surface 810 of spacer 100. More precisely, as drive screw 806 is turned, wedge 812 abuts against the bowed portion of upper anchor 802 and lower anchor 804. As wedge 812 abuts against the bowed portion of the anchors, the inclined surface of wedge 810 slides along the surface of upper anchor 802 and lower anchor 804. The sliding motion applies pressure to the surfaces of the anchors, thereby forcing both upper anchor 802 and lower anchor 804 to radially extend outside of the openings of spacer 100 and into their respective intervertebral bodies.

In a further embodiment, as depicted in FIGS. 9A-9H, the anchoring device has a drive plate 906 from which upper anchor 902 and lower anchor 904 extend.

The drive plate of FIG. 9A includes through-hole 908 arranged at its central axis. The drive plate can be divided into four quadrants, with through-hole 908 being the origin point, like in a two-dimensional Cartesian plane. Upper anchor 902 extends from a first one of the quadrants (e.g., Quadrant I in a two-dimensional Cartesian plane), while lower anchor 904 extends from a second one of the quadrants (e.g., Quadrant III in the two-dimensional Cartesian plane), wherein the first and second quadrants are diagonally located from each other on drive plate 906. Although the anchors have been described as having a specific arrangement on drive plate 906, it will be clear to those skilled in the art after reading this disclosure that upper anchor 902 and lower anchor 904 can be arranged anywhere on the drive plate without departing from the scope of the present invention.

As further depicted in FIG. 9A, each of upper anchor 902 and lower anchor 906 has a pointed tip and a plurality of projections arranged on their lateral surfaces. The plurality of projections can be, for example, and without limitation, barbs that are angled away from the point in which the anchors penetrate into their respective vertebras. The barbs are advantageous because they make it difficult for the anchors to come loose, thus ensuring that the spacer is securely stabilized between the vertebras after implantation. FIG. 9A also depicts a pair of oppositely positioned grippers of holder 910 gripping onto the lateral surfaces of drive plate 906.

Turning now to FIG. 9B, while drive plate 906 is gripped by holder 910, a surgeon can position the grippers of holder 910 to also grip onto endplate 912 of spacer 900. Once endplate 912 is gripped by the surgeon, a driver 914 can be inserted into holder 910, which passes through through-hole 908 of drive plate 906. The driver engages one end of drive screw 916 (shown in FIG. 9C) housed within spacer 900. Once the driver has engaged the drive screw, the surgeon can turn driver 914 so that drive screw 916 can be threaded into the body of wedge 918. This causes wedge 918 to move backwards towards the proximal end of spacer 900, which in turn causes superior surface 920 and inferior surface 922 of the spacer to slide along the inclined surface of wedge 918. This can be seen more clearly in FIGS. 9C and 9D. As superior surface 920 and inferior surface 922 radially extend in opposite directions of each other, upper anchor 902 and lower anchor 904 engage upper guide 924 and lower guide 926 of spacer 900. As shown in FIG. 9D, the tips of upper anchor 902 and lower anchor 904 do not extend past the profile of teeth 928 of spacer 900, even after superior surface 920 and inferior surface 922 have been fully extended.

Once the superior and inferior surfaces of spacer 900 have been fully extended, the surgeon can now retract driver 914 and insert pull screw 930 (i.e., anchor driver) as shown in FIG. 9E. Pull screw 930 is physically adapted to be inserted through through-hole 908 and into the threaded hole of drive screw 916. Pull screw 930 can now be threaded to advance drive plate 906 towards the proximal end of spacer 900, which causes upper anchor 902 and lower anchor 904 to respectively slide along upper guide 924 and lower guide 926 as the drive plate is advanced towards the proximal end of the spacer. As upper anchor 902 and lower anchor 904 slide along their respective guides, the anchors simultaneously and radially extend away from spacer 900 and into their respective intervertebral bodies. Pull screw 930 is threaded by the surgeon until drive plate 906 is fully seated against endplate 912. Not only does threading pull screw 930 in this way fully deploy the anchors into their respective intervertebral bodies, it also locks the anchors to spacer 900 in a deployed position, as shown in FIGS. 9F-9H.

FIG. 10 depicts a spacer-anchor combination in accordance with an alternative embodiment of the present invention. More specifically, the figure depicts spacer 1000, a plurality of upper anchors 1002, worm 1004, and gear 1006. In accordance with this embodiment, the worm is physically adapted to turn the gear, but the gear cannot turn the worm. This is because the angle on the worm is so shallow that, when the gear tries to spin it, the friction between the gear and the worm holds the worm in place. With this in mind, a surgeon can implant spacer 1000 in the disc space of adjacent vertebras. The surgeon can then use a tool to turn worm 1004 in order to rotate gear 1006 in a particular direction. As the gear rotates, upper anchors 1002 are simultaneously deployed into an intervertebral body. Once deployed, pressure from adjacent vertebras compressing down onto gear 1006 will not cause the gear to rotate. This is because, as discussed above, the angle on the worm is so shallow that the friction between the gear and the worm essentially locks the worm in place. Accordingly, upper anchors 1002 will be locked in their deployed position until worm 1004 is operated.

It is to be understood that the disclosure describes a few embodiments and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims. 

What is claimed is:
 1. An intervertebral fusion device comprising: a spacer, having a superior surface, an inferior surface, and opposing lateral surfaces, the spacer adapted to be implanted between an upper vertebral body and a lower vertebral body, the spacer having a central longitudinal axis that equally bisects a front end and a rear end of the spacer; a through-hole configured to receive bone graft material and configured to extend through the superior surface, the inferior surface, and the opposing lateral surfaces; and an anchoring device having an upper anchor with first and second lateral projections and a lower anchor with first and second lateral projections, wherein the upper and lower anchors are adapted to be simultaneously deployed into their respective upper and lower vertebral bodies when force is applied thereto, wherein the spacer has an upper guide and a lower guide that are adapted to respectively guide the deployment of the upper and lower anchors into their respective vertebral bodies, wherein each of the upper and lower guides are aligned with the central longitudinal axis of the spacer such that the upper and lower guides are each equally bisected by the central longitudinal axis, wherein the spacer includes a first plurality of through openings extending entirely through the opposing lateral surfaces and into the upper guide and a second plurality of through openings extending entirely through the opposing lateral surfaces and into the lower guide, wherein the first and second lateral projections of the upper anchor are receivable in the first plurality of through openings and the first and second lateral projections of the lower anchor are receivable in the second plurality of through openings to lock the upper and lower anchors to the spacer.
 2. The intervertebral fusion device of claim 1, wherein the upper and lower anchors in an undeployed state are disposed entirely within the spacer; and distal ends of the upper and lower anchors in a deployed state are radially extended outside of the spacer.
 3. The intervertebral fusion device of claim 1, wherein the upper and lower anchors are separate elements that slide independently of each other along their respective upper and lower guides when force is applied to the upper and lower anchors.
 4. The intervertebral fusion device of claim 1, wherein each of the upper and lower guides has an inclined surface that presses against a respective one of the upper and lower anchors to deploy them into their respective vertebral bodies.
 5. The intervertebral fusion device of claim 4, wherein the upper and lower anchors respectively have a contour that is substantially the same as the inclined surface of the upper and lower guides; and the inclined surface of the upper and lower guides is curvilinear.
 6. The intervertebral fusion device of claim 1, wherein each of the upper and lower guides has a pair of oppositely positioned lateral recesses that receive lateral sides of a respective one of the upper and lower anchors.
 7. The intervertebral fusion device of claim 1, wherein each of the upper and lower anchors include a pair of flexible prongs.
 8. The intervertebral fusion device of claim 1, wherein each of the upper and lower anchors include a pair of flexible prongs; and for each of the flexible prongs, the spacer has a chamfer positioned proximally of the respective recess to cause a respective one of the prongs to laterally flex inwardly.
 9. The intervertebral fusion device of claim 1, wherein the spacer includes a pair of oppositely positioned lateral surfaces, with each of the surfaces having a recess for receiving a corresponding rib of a gripper of an implantation instrument.
 10. An intervertebral fusion device system, comprising: the intervertebral fusion device of claim 1; and an implantation instrument with an anchor driver for applying force to the upper and lower anchors, wherein the anchor driver is advanced between a pair of leaf springs of the implantation instrument to cause a first gripper and a second gripper to respectively grip a first lateral surface and a second lateral surface of the spacer.
 11. The intervertebral fusion system of claim 10, wherein the first and second grippers are respectively adapted to pivot inwardly about a first pivot point and a second pivot point as the anchor driver is advanced between the pair of leaf springs.
 12. The intervertebral fusion device of claim 1, wherein the upper and lower anchors are housed within the spacer; and the upper and lower anchors radially deploy out of the spacer into their respective intervertebral bodies when an anchor driver is forcibly advanced towards a bowed portion of the upper and lower anchors.
 13. The intervertebral fusion device of claim 1, wherein each of the upper and lower anchors has a pointed tip and a plurality of barbs; and the barbs are arranged on lateral surfaces of the upper and lower anchors. 